The present invention is in the field of electronic equipment and, more particularly, electronic equipment which generates heat during its operation.
Certain types of electronic equipment may embody components which generate heat during their operation. Very often these heat-generating components may perform power supplying functions. It is common practice to integrate power-supplying functions along with logic functions in many types of electronic equipment. Such integration may permit electronic functions to be performed in compact and light weight assemblies. Compactness and light weight may be particularly useful in electronic equipment used in aircraft or space vehicles.
Electronic assemblies with integrated power-supplying components may be constructed with integrated heat-absorbing elements. Such heat-absorbing element may be referred to as cold plates. A typical cold plate, used for example in an aircraft, may comprise a metallic plate onto which heat-generating electronic devices are attached. The cold plate may be cooled by a flow of cooling fluid which may be a gas or a liquid. As the fluid flows, excess heat produced by the electronic assembly is carried away.
In some instances, it may be desirable to constrain the cooling fluid as it flows. In these cases, the cold plate may comprise an enclosure. The enclosure may have an entrance port and an exit port for cooling fluid. To enhance cooling, the fluid may be admitted to the cold plate at a high pressure, in the order of about 100 psi to about 300 psi. To withstand these high fluid pressures, the cold plate enclosure must be constructed with substantial mechanical strength. One obvious method for achieving mechanical strength is through use of a thick-walled enclosure. But thick-walled enclosures are inherently heavy and are therefore undesirable for aircraft applications.
To address the issue of desired mechanical strength and low weight, prior-art designers of aircraft cold plates have employed a composite configuration. In this prior-art configuration a metallic fin structure is sandwiched between two relatively thick (about 0.25 inch) metallic plates. The plates and fins are brazed together at a temperature of about 1400° F. to form a cold plate assembly. After brazing the cold-plate assembly may be heat treated at a temperature of about 1100 F. During exposure to these high temperatures the cold-plate assembly may become distorted or warped. It may lose some of its “flatness”. Flatness of a cold plate is important because effective heat transfer from electronic devices into the cold plate requires maximum contact between a surface of the electronic device and the cold plate. If the cold plate is not flat the required contact may be diminished.
Restoration of flatness in prior art cold plates, may be achieved by machining an outer surface of the metallic plates and making them thinner. Typically the plate may be machined to reduce its thickness for about 0.25 inch to about 0.1 inch. This machining step may re-introduce flatness but it is costly and difficult to perform.
In some cold plate assemblies, mechanical strength may be enhanced by using bolts to hold the metallic plates and the fin together. Use of bolts, of course, requires creation of holes through which the bolts may pass. Each of these holes presents an opportunity for leakage of the cooling fluid. Consequently bolted cold plate assemblies require elaborate sealing structures around the bolts in order to prevent the cooling fluid leakage around the bolts.
When prior-art enclosed cold plates were used for cooling electronic assemblies, electronic devices were typically placed on only one side of a cold plate. It is very difficult and cumbersome to produce and use vias through an enclosed cold plate. In brazed constructions via apertures are subject to blockage during brazing. In bolted assemblies each via required a dedicated seal. Consequently, electronic assemblies constructed on enclosed cold plates consumed undesirable large areas because electronic devices could not be placed on both sides of an enclosed cold plate and interconnected through the cold plate.
As can be seen, it would be desirable to provide cooled electronic assemblies with economical and lightweight enclosed cold plates Additionally, it would be desirable to provide cooled electronic assemblies with electrically interconnected electronic devices placed on both sides of an enclosed cold plate.